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Brain Food: Valentine's Day In The Natural World

Trees For Life

As we get ready to celebrate Valentine's Day, Northern Arizona University ecology professor Nancy Collins Johnson reminds us that we can learn a lot about relationships from nature. Collins is a soils expert who studies mycorrhizal symbiosis - or, healthy relationships between fungi and the roots of plants.

Johnson says, "here in Flagstaff, our pine trees are the most obvious example of mycorrhizal associations. Pines cannot survive for long without their symbiotic partnerships with fungi. Many tree species form "trading partnerships" with fungi: The fungus supplies its plant host with essential nutrients and water. In return, the plant gives the fungus carbon in the form of sugars."

These fungal partners, she says, have microscopic hyphae. These act like thin arms that reach out and grab mineral nutrients like nitrogen, phosphorus, copper and zinc from the soil and transfer them to the trees.

"If you use a microscope," Johnson says, "to look at a handful of soil taken out of your garden, or a forest, or even a desert, you'll probably see a mile of the hyphae - thin, thread-like structures that the fungus uses to forage in the soil for minerals and to gather water."

Johnson says these kinds of relationships have flourished for more than 460 million years.

"This is a very close and ancient partnership," Johnson says. "More than 90% of all plant species form some sort of mycorrhizal associations with fungi."

So, just as with human relationships, plant relationships require a health balance of give and take.

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